Plotter drum mounting system

ABSTRACT

A mechanical detent having a limited engagement length may be used to precisely position one rotatably adjustable member relative to another. Such an arrangement may be used to reestablish the correct axial loading when installing a plotter drum after it has been removed.

United States Patent Inventor Joseph R. Read Anaheim, Calif.

Appl. No. 886,915

Filed Dec. 22, 1969 Patented Dec. 28, 1971 Assignee California Computer Products, Inc.

Anaheim, Calif.

PLOTTER DRUM MOUNTING SYSTEM 3 Claims, 2 Drawing Figs.

US. Cl 346/136, 29/111, 242/684 Int. Cl ..G01d 15/28 Field of Search 346/136,

[5 6] References Cited UNITED STATES PATENTS 1,858,391 5/1932 Clauberg... 242/68.4 2,686,012 8/1954 Gabelet al 242/55 Primary Examiner-Joseph W. Hartary Attorney-John A. Duffy f'll PLOTTER DRUM MOUNTING SYSTEM BACKGROUND FOR THE INVENTION Conventional incremental plotters are of two basic types, namely, flat bed and drum. In the latter category, the plotting is carried out on a continuous strip of paper, a portion of which lays over a cylindrical plotting drum which is rotated in accordance with external commands to effectuate the required plotting motion in one dimension. Motion in the other direction is accomplished by moving a plotting stylus in a direction parallel with the cylindrical drum axis. The drum itself may be rotated in either direction, and its surface provides the support for the paper upon which the stylus moves. In such a plotter, it is necessary that the drum be mounted concentric with the cylindrical axis, this normally being effected by rigid supports at each end of the drum. In prior art plotters of this type, the drum is hard mounted in the sense that it cannot be removed and reinstalled in the supports without subsequent realignment. What is actually desired, however, is an arrangement which will allow the drum to be removed and installed without special tools, and which does not require subsequent realignment or in any way alter the dynamic characteristics as by changing axial loading pressure and the like. Accordingly, a primary object of the present invention is to provide an arrangement for removing and installing a plotter drum without the use of special tools.

It is a further object of the invention to provide an arrangement for quickly aligning a plotter drum with respect to its drive mechanism.

It is another object of the invention to provide a means for easily removing and installing a conventional plotter drum so as to retain the initial alignment and axial loading.

Other objects and advantages of the present invention will be obvious from the detailed description of a particular embodiment given hereinbelow.

SUMMARY OF THE INVENTION The present invention comprises an assembly for reinstalling a plotter drum so as to duplicate the original axial loading conditions. This is accomplished by a limited movement manual detent. When the axial loading is initially established at the factory, the detent is used to retain the proper axial load by locking a rotatably adjustable member relative to a fixed support. Because of the limited detent movement, the detent will only engage the detent hole when the adjustable member is returned to its initial position. Consequently, the original loading conditions may be reestablished.

DESCRIPTION OF THE DRAWING DESCRIPTION OF THE DRAWING FIG. 1 is a cross-sectional view illustrating the operative features of the plotter drum mounting system.

FIG. 2 shows a end view of the mounting system.

DESCRIPTION OF A PREFERRED EMBODIMENT Adverting to the drawing in FIG. 1, a preferred embodiment of the invention comprises a bearing post 1 and adjustment ring 2, an adjustment shaft 5, a detent flange 3, and a pin 7. These parts are assembled to effect the positional relationships shown in the drawing as follows: First, the adjustment ring is attached to the adjustment shaft 5 by screws 14, the adjustment shaft 5 being then screwed into the side support 6 until the adjustment ring 2 is touching the side support 6. The

drum assembly, comprised of the drum 8, drum endbell12, and bearing 13 is then inserted into the left-hand support location (not shown) and then brought into such a position that the bore of bearing 13 is in line with the bearing post 1. In this position the adjustment ring 2 may then be rotated to unscrew the adjustment shaft 5 from the side support 6 until the bearing post 1 enters the bore of bearing 13. With further rotation of the adjustment ring 2 the axial load on the drum assembly increases as the bearing post 1 engages bearing 13. Part A" of the following description will describe how factory adjustment is initially made for this pressure, and part B" will describe how subsequent drum replacement can be made by automatically returning to this same adjustment.

Part A. The adjustment ring 2 is rotated until a predetermined axial pressure is imposed on the drum assembly. (The method for determining this pressure is irrelevant to this discussion.) When the desired pressure has been obtained, the rotation of adjustment ring 2 is discontinued. The detent flange 3 is then slid over the right-hand end of the adjustment shaft 5 and rotated until the detent hole 11 engages with the end of pin 7. It is noted that pin 7 is spring-loaded into side support 6 by virtue of spring 10 and snapring 9. When the detent flange 3 is thus positioned, it is integrally locked to adjustment shaft 5 by setscrew 4. In this position it is not possible to further rotate adjustment ring 2 in either direction without the retraction of pin 7 from detent hole 11. This completes the factory adjustment.

Part B. When a drum assembly has been factory installed as per part A above, it is possible to remove the drum by retracting pin 7 and rotating adjustment ring 2 in a direction toward the side support. The length of engagement of pin 7 into detent hole 11 is such that it will not reengage after one complete revolution of the detent flange 3. Hence, once the detent hole 11 has rotated away from pin 7, the pin 7 may be relaxed against the detent flange 3 as the disengagement continues. When the adjustment ring 2 is sufficiently close to the side support 6 the drum may be removed and a second drum positioned for installation. The adjustment mechanism is now screwed out from the side support 6 to again engage bearing 13. Rotation of adjustment ring 2 is continued until the detent hole 11 is congruent with the end of pin 7, at which time the pin 7 will engage the hole and inhibit further rotation. In this position the second drum is loaded under precisely the same pressure as the first.

Should operation wear occur, this mechanism will allow for subsequent repositioning of the detent location. This can be accomplished by loosening setscrew 4, and either advancing or retracting adjustment ring 2 to the point of desired load. This new adjustment position may then be secured by retightening set screw 4.

This invention provides a positive and highly repeatable means of loading the drum to factory specifications while maintaining the necessary degree of concentricity. Although a preferred embodiment of the invention has been shown and illustrated, the invention is not limited thereto, and it will be understood that numerous changes, modifications and substitutions may be made without departing from the spirit of the invention.

I claim:

1. An arrangement for mounting a plotting drum comprising:

an adjustment ring;

a threaded adjustment shaft;

means for attaching said adjustment ring to one end of said adjustment shaft;

a detent flange having a detent hole;

means for attaching said detent flange to the other end of said adjustment shaft;

a side support having a threaded opening adapted to receive said threaded adjustment shaft whereby said shaft may be turned relative to said side support so as to axially move said adjustment ring;

means for locking said adjustment ring after the desired axial loading has been established;

means for removing said drum without changing said adjustment ring; and

means for reinstalling said drum to establish the original axial loading conditions without changing said adjustment ring.

2. The apparatus recited in claim 1 wherein said means for locking said adjustment ring comprises:

means for limiting the travel of said detent pin to less than the axial travel distance produced by a revolution of the adjustment shaft relative to said support whereby the location of said adjustment ring relative to said side support may be reestablished after said drum has been removed and replace. 

1. An arrangement for mounting a plotting drum comprising: an adjustment ring; a threaded adjustment shaft; means for attaching said adjustment ring to one end of said adjustment shaft; a detent flange having a detent hole; means for attaching said detent flange to the other end of said adjustment shaft; a side support having a threaded opening adapted to receive said threaded adjustment shaft whereby said shaft may be turned relative to said side support so as to axially move said adjustment ring; means for lOcking said adjustment ring after the desired axial loading has been established; means for removing said drum without changing said adjustment ring; and means for reinstalling said drum to establish the original axial loading conditions without changing said adjustment ring.
 2. The apparatus recited in claim 1 wherein said means for locking said adjustment ring comprises: a detent pin mounted on said side support and juxtaposed relative to the detent hole in said detent flange; bias means to cause said detent pin to engage the detent hole in said detent flange whereby said detent flange, adjustment shaft and adjustment ring may be locked relative to said side support.
 3. The apparatus recited in claim 2 wherein is included a means for limiting the travel of said detent pin to less than the axial travel distance produced by a revolution of the adjustment shaft relative to said support whereby the location of said adjustment ring relative to said side support may be reestablished after said drum has been removed and replaced. 